The present invention relates generally to optical networks, and more particularly, to adaptive coded-modulation for intelligent optical transport networks.
The following references are referred to in this background discussion:    [1] M. Arabaci, I. B. Djordjevic, R. Saunders, and R. M. Marcoccia, “Polarization-multiplexed rate-adaptive non-binary-LDPC-coded multilevel modulation with coherent detection for optical transport networks,” Optics Express, vol. 18, pp. 1820-1832, January 2010.    [2] I. B. Djordjevic, “Adaptive LDPC-Coded Multilevel Modulation with Coherent Detection for High-Speed Optical Transmission,” IEEE Photonics Society Summer Topicals 2009, 20-22 Jul. 2009, Newport Beach, Calif., Paper no. WC1. 2.    [3] I. B. Djordjevic, M. Arabaci, and L. Minkov, “Next Generation FEC for High-Capacity Communication in Optical Transport Networks,” IEEE/OSA J. Lightw. Technol., vol. 27, no. 16, pp. 3518-3530, Aug. 15, 2009.
Future intelligent optical transport networks (OTNs) should possess the capability of dynamic data rate adjustment. One solution is to adjust data rate by changing the overhead of the adopted forward-error-correction (FEC) codes while keeping other system configurations unchanged. Meanwhile, to meet the increasing high demand on data rate, low-density-parity-check (LDPC) codes have been proved to be promising candidates for high-speed OTNs. Therefore rate-adaptive LDPC-coded modulation [1,2], becomes an essential component for the future OTNs.
Rate-adaptive techniques based on LDPC codes being able to adjust data rate dynamically by changing the overhead of LDPC codes have been proposed recently in [1,2]. However, since low-density parity-check LDPC codes with different overheads and code rates have been used, the transmitter and receiver have to be designed to support all the LDPC codes resulting in very high complexity and costs of hardware. Although quasi-cyclic LDPC (QC-LDPC) codes can be used to reduce the encoder and decoder hardware complexity with minimal cost [3], no practical solution has yet been proposed to reduce the complexity of the rate-adaptive LDPC-coded modulation schemes.
Accordingly, there is a need for adaptive coded-modulation for intelligent optical transport networks.